KR20020043841A - Device and method for maximizing the efficiency of power amplifier - Google Patents

Abstract

PURPOSE: A control apparatus and method for maximizing efficiency of power amplifier are provided to maximize efficiency of a power amplifier in a wireless communication terminal and increase a communication time of the wireless communication terminal. CONSTITUTION: A received strength signal indicator(305) detects a strength of a received signal and output a detected result to a controller(304). The controller(304) receives the detected result from the received strength signal indicator(305) and outputs a current and a voltage for controlling a power amplifier. The power amplifier includes first and second power amplifiers(302,303) which are connected to each other in series. The first power amplifier(302) is coupled with a high frequency signal input terminal(RFin). The second power amplifier(303) is coupled with a high frequency signal output terminal(RFout). Each of the first and second power amplifiers(302,303) includes a power supply input terminal and a bias control terminal(306). A variable power supply(301) supplies a power supply corresponding to a voltage control signal from the controller(304) to the power supply input terminal of each of the first and second power amplifiers(302,303).

Description

DEVICE AND METHOD FOR MAXIMIZING THE EFFICIENCY OF POWER AMPLIFIER}

The present invention relates to a power amplifier of a wireless communication terminal, and more particularly, to an apparatus and method for controlling a transmission output level in order to maximize the efficiency of the power amplifier.

In general, a terminal (hereinafter referred to as a "wireless communication terminal") of a wireless communication system such as a code division multiple access (CDMA) method or a personal communication services (PCS) method is a high frequency (RF) radio. Frequency) signal is transmitted through the antenna, and a signal from the base station is received through the antenna. For this transmission and reception operation, a transmission amplifier of a wireless (mobile) communication terminal is provided with a power amplifier as is well known.

The power amplifier (PA) occupies a large portion of the characteristics and power consumption of the system, and is not always driven at the maximum output power, but its output power level according to the distance to the base station and the user's moving speed. Becomes variable. When the distance between the base station and the wireless communication terminal is close, that is, when the strength of the received signal is large, the output power level of the power amplifier is relatively decreased. On the other hand, when the wireless communication terminal moves to the furthest place within the cell radius, that is, when the received signal strength is small or the user's moving speed is increased, the power amplifier is a high frequency signal close to the maximum output power level. Will be sent.

1 is a view showing the configuration of a power amplifier control apparatus according to the prior art.

Referring to FIG. 1, the controller 205 outputs a control signal according to the level of a received signal, which is applied to the current bias circuit 204 to control the power amplifiers 201 and 202. The control signal is a signal consisting of 1 bit or 2 bits. In the case where a 1-bit control signal is used, the power amplifier emits high power when the received signal level is above a certain threshold and low power when below a certain threshold. On the other hand, when a 2-bit control signal is used, the transmission power is determined by three threshold values.

Thus, when using 1 bit or 2 bit as a control signal for controlling the bias of the power amplifier, there are only a few bias states, so it is impossible to make an optimum bias for all transmission output levels. There is this. These disadvantages lower the efficiency of the power amplifier and shorten the talk time of the wireless (mobile) communication terminal.

Accordingly, an object of the present invention is to provide an apparatus and method for maximizing the efficiency of a power amplifier in a wireless communication terminal.

Another object of the present invention is to provide a power amplifier control apparatus and method for increasing the talk time of a wireless communication terminal.

It is still another object of the present invention to provide an apparatus and method for minimizing power consumption of a power amplifier in a range satisfying linearity required for a wireless communication terminal by controlling bias current and voltage according to a transmission output level.

In order to achieve these objectives, the present invention sets an appropriate bias for all output power levels in the transmission range to control the power amplifier to be used more efficiently. The received signal strength detector of the power amplifier control device according to the present invention detects the strength of the received signal. A signal generator generates a pulse density modulation (PDM) signal corresponding to the detected strength of the received signal and changes linearly with the strength of the received signal, and uses this PDM signal to control the bias of the power amplifier. Occurs. The power amplifier control device includes an adder for adding the received signal strength and a predetermined closed loop power control value, a lookup table for outputting a digital value corresponding to the addition result by the adder to the input of the signal generator, And a limiter connected between the adder and the lookup table, for limiting the addition result to a value within a preset range.

1 is a view showing the configuration of a power amplifier control device according to the prior art.

2 is a view showing the configuration of a power amplifier control device according to an embodiment of the present invention.

3 is a view showing a specific configuration of the control unit shown in FIG.

4 is a view for contrasting the efficiency according to the output power of the power amplifier according to the prior art and the embodiment of the present invention.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings. It should be noted that reference numerals and like elements among the drawings are denoted by the same reference numerals and symbols as much as possible even though they are shown in different drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

2 is a view showing the configuration of a power amplifier control device according to an embodiment of the present invention. The power amplifier control device is characterized in that the bias is continuously controlled in order to obtain the maximum efficiency according to the output level.

Referring to FIG. 2, the power amplifier control apparatus according to the embodiment of the present invention includes a variable power supply unit 301, a first power amplifier (PA1) 302, a PA2 303, a controller 304, and a received signal strength ( RSSI: Received Strength Signal Indicator (RSI) detector. The RSSI detector 305 detects the strength of the received signal and outputs the detection result to the controller 304. The controller 304 inputs a detection result by the RSSI detector 305, and outputs a signal Vbias_cntl for controlling the current of the power amplifier and a signal for controlling the voltage. In addition, the controller 304 outputs a signal for controlling an AGC amplifier (not shown). The controller 304 is configured as shown in FIG. 3 to be described later. The power amplifier is configured by connecting a first power amplifier 302 and a second power amplifier 303 in series. The first power amplifier 302 is connected to a high frequency signal input terminal RFin, and the second power amplifier 303 is connected to a high frequency signal output terminal RFout. The power amplifiers 302 and 303 include a power input terminal and a bias control terminal 306, respectively. The variable power supply unit 301 provides a power supply Vc corresponding to the voltage control signal from the control unit 304 to the power input terminals of the power amplifiers 302 and 303.

3 is a diagram illustrating a detailed configuration of the controller 304 shown in FIG. 2.

Referring to FIG. 3, the controller 304 includes power amplifier look-up tables (PALUT RAM) 401, 402, pulse density modulation (PDM) signal generators 403, 404, and transmission gain limitation. A TX_GAIN_LIMIT 405, a closed-loop power control value storage unit 406, and an adder 407.

The adder 407 adds the strength of the received signal detected by the RSSI detector 305 and a predetermined closed loop power control value, and outputs the addition result. The transmission gain limiter 405 limits the output of the adder 407 so as not to exceed a preset range. The output of the transmission gain limiter 405 is applied to the first lookup table 401 and the second lookup table 402. Each of the lookup tables 401 and 402 outputs a value corresponding to the output of the transmission gain limiter 405. The lookup tables 401 and 402 store output values corresponding to a series of input values. In this case, the first lookup table 401 outputs a digital value for controlling the voltages of the power amplifiers 302 and 303, and the second lookup table 402 outputs a digital value for controlling the currents of the power amplifiers 302 and 303. The first PDM signal generator 403 generates a first PDM signal corresponding to the output of the first lookup table 401, and the second PDM signal generator 404 generates a second PDM signal corresponding to the output of the second lookup table 402. The first PDM signal is a signal for controlling bias voltages of the power amplifiers 302 and 303, and the second PDM signal is a signal for controlling bias currents of the power amplifiers 302 and 303.

As described above, the present invention operates as follows as a control device for controlling the bias according to the output level of the power amplifier of the wireless communication terminal to maintain the linearity inherent to the amplifier and to minimize the DC power consumption.

First, the voltage and current bias are set for the overall output level of the power amplifier according to the following principle.

Maintain the original linear characteristics of the power amplifier (eg, Adjacent Channel Power Rejection (ACPR), 3rd order Intermodulation Distortion (IMD3)).

2. Avoid sudden changes in bias current and voltage. As much as possible, the current control signal Vbias_cntl and the driving voltage Vc change linearly with the output level, and the bias is selected in a range where the bias current and the voltage gradually change gradually. This makes it simple and reliable to control the voltage and current according to the output level change. Sudden changes in the bias voltage current can cause the power amplifier to malfunction in the transient state of these biases.

3. Maximize the efficiency of the power amplifier when the two conditions above are met.

The control voltage for applying the voltage and the current bias determined as described above is generated by the controller 304 shown in FIG. 2.

4, 403 and 404 are PDM signal generators, and output voltages change according to input values. This output voltage allows you to control the voltage and current bias of the power amplifier. Therefore, an appropriate value should be put in the lookup tables 401 and 402 so that the PDM control voltage for the desired transmit output power can be obtained.

Since the transmission output power is determined by the reception signal level, the output value of the RSSI detector 305 indicates the addresses of the lookup tables 401 and 402. At this time, the output value of the RSSI detector 305 is considered to be a value 406 by the closed loop power control (Closed Loop power control), so as not to exceed the output power limit 405. The input values of the PDM signal generators 403 and 404 are determined by calculating the values stored in the addresses of the respective lookup tables 401 and 402, and the PDM control voltages corresponding to the input values are generated by the PDM signal generators 403 and 404. The voltage and current bias of the power amplifiers 302 and 303 is controlled. Voltage and current bias control is continuously controlled over all transmit power level ranges with respective lookup tables 401,402 and PDM signal generators 403,404.

4 is a view for contrasting the efficiency according to the output power of the power amplifier according to the prior art and the embodiment of the present invention.

Referring to FIG. 4, it can be seen that the present invention maintains the linear efficiency as the output power Pout of the power amplifier changes. On the other hand, it can be seen that the prior art does not maintain linear characteristics.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention uses the power amplifier of the mobile communication terminal, and maintains the linear characteristics even at a low output level of voltage and current bias by controlling continuously to improve the efficiency to save the power consumption of the terminal There is this.

Claims (12)

An apparatus for controlling output power of a power amplifier in a wireless communication terminal having a power amplifier for power amplifying a signal for transmission, the apparatus comprising: A received signal strength detector for detecting the strength of the received signal; Generating a pulse density modulation (PDM) signal corresponding to the detected intensity of the received signal and varying linearly with the intensity of the received signal, and generating the PDM signal as a signal for controlling the bias of the power amplifier; Said device comprising a signal generator. The method of claim 1, An adder for adding the received signal strength and a predetermined closed loop power control value; And a lookup table for outputting a digital value corresponding to the addition result by the adder to the input of the signal generator. 3. The apparatus as claimed in claim 2, further comprising a limiter connected between the adder and the lookup table and for limiting the addition result to a value within a preset range. A method for controlling output power of a power amplifier in a wireless communication terminal having a power amplifier for power amplifying a signal for transmission, the method comprising: Detecting the strength of the received signal; Generating a pulse density modulation (PDM) signal corresponding to the detected intensity of the received signal and varying linearly with the intensity of the received signal, and outputting the PDM signal as a signal for controlling the bias of the power amplifier; Said method comprising a process. The method of claim 4, wherein Adding the strength of the received signal and a predetermined closed loop power control value; And outputting a digital value corresponding to the addition result as an input for generating the PDM signal. The method as claimed in claim 5, further comprising limiting the addition result to a value within a preset range. An apparatus for controlling output power of a power amplifier in a wireless communication terminal having a power amplifier for power amplifying a signal for transmission, the apparatus comprising: A received signal strength detector for detecting the strength of the received signal; A signal generator corresponding to the detected intensity of the received signal and generating a voltage pulse density modulation (PDM) signal and a current PDM signal that change linearly with the intensity of the received signal; A variable power supply for supplying power corresponding to the voltage PDM signal to the power amplifier, And the output power of the power amplifier is controlled by the power supplied from the variable power supply and the current PDM signal. The method of claim 7, wherein An adder for adding the received signal strength and a predetermined closed loop power control value; A first lookup table for outputting the voltage PDM signal by providing a digital value corresponding to the addition result by the adder to the input of the signal generator; And a second lookup table for outputting the current PDM signal by providing a digital value corresponding to the addition result by the adder to the input of the signal generator. 9. The apparatus as claimed in claim 8, further comprising a limiter connected between the adder and the lookup table, the limiter for limiting the addition result to a value within a preset range. A method for controlling output power of a power amplifier in a wireless communication terminal having a power amplifier for power amplifying a signal for transmission, the method comprising: Detecting the strength of the received signal; Generating a voltage pulse density modulation (PDM) signal and a current PDM signal corresponding to the detected intensity of the received signal and varying linearly with the intensity of the received signal; Supplying a power corresponding to the voltage PDM signal to the power amplifier, The output power of the power amplifier is controlled by a power source corresponding to the voltage PDM signal and the current PDM signal. The method of claim 10, Adding the strength of the received signal and a predetermined closed loop power control value; Reading a digital value corresponding to the addition result from a first lookup table storing an output digital value corresponding to a series of input values, and outputting the digital value corresponding to the voltage PDM signal generation; Reading a digital value corresponding to the addition result from a second lookup table storing an output digital value corresponding to a series of input values, and outputting the current PDM signal for generation. The method. The method as claimed in claim 11, further comprising limiting the addition result to a value within a preset range.